German Patent No. 35 45 716 describes an arrangement for controlling the propulsion of motor vehicles by decreasing the output torque of the vehicle engine or braking the appropriate wheel to prevent undesired spinning of the driven wheels of the vehicle when their slip exceeds a set threshold. For this purpose, the lateral acceleration of the vehicle is measured using a cornering detection arrangement and analyzed in an appropriate device.
The known device operates independently of the instantaneous steering-wheel angle arising from the instantaneous driving situation of the vehicle, especially in a skid (unstable driving condition). If the vehicle tries to spin out, the driver automatically countersteers to keep the vehicle under control. This effect is not taken into account.
The method and the device according to the present invention have the advantage that an unstable driving condition of the motor vehicle can be detected using a simple steering-angle sensor without the need for any elaborate measures such as road maps and measuring the radius of the curve.
It is particularly advantageous to weight the computed difference between the measured and the computed lateral acceleration using a rating factor in such a way that a clear distinction can be drawn between a stable and an unstable driving condition of the motor vehicle. If the rating factor is 1, a stable driving condition is present. If the value is 0, the driving condition is unstable. A simple corrective signal can advantageously be derived from this and displayed or supplied to additional control units for automatic transmission, suspension control, etc.
To prevent any abrupt changes in a setpoint value within the transition range between stable and unstable driving conditions, this range is advantageously realized as a slope.
It is further advantageous that the rating factor is output visually through a display element or acoustically through a speaker, so that the driver is alerted to a critical driving condition of the motor vehicle.
A further advantage is seen in the fact that the rating factor is supplied to a further control unit, which is implemented, for example, for suspension control or an automatic transmission. In this way, for example, the automatic transmission can be prevented from shifting into the next-higher or next-lower gear during cornering.
It is favorable, furthermore, that the computed lateral acceleration is weighted with model-specific data of a specific motor vehicle. This makes it possible to adapt the lateral acceleration, in combination with the road speed, to the specific characteristics of the vehicle.